This application claims the priority of 198 18 866.8-14, filed Apr. 28, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a selection system for an automatic motor vehicle transmission, and more particularly, to a selection system comprising a selector lever which, for selecting shifting positions of the motor vehicle transmission, is arranged to be manually adjustable along a defined moving path in a lever transverse direction to multiple positions (P, R, N, D). A first locking body is arranged to be movable about a rotation axis in a moving direction which extends at a right angle with respect to the direction of a movement of the selector lever to be blocked. A locking surface contour has at least a first oblique locking surface which, in the locked position of the selector lever, is situated forwardly of the selector lever in a moving path thereof and extends diagonally with respect to the moving direction of the selector level and the moving direction of the first locking body such that a manual force component on the selector level is divided on the oblique locking surface into a first force component which extends at a right angle to the oblique locking surface and into a second force component which is directed at a right angle with respect to the manual force component. The second force component is directed in the unlocking moving direction of the first locking body, and a second locking body is arranged to be movable relative to the first locking body and is movable by an actuator arrangement as a function of defined operating conditions automatically between a first position which locks the first locking body in a defined position and a second position which does not lock the first locking body.
A selection system is described in DE 41 20 379 A1. There, a rotation axis of a first locking element is arranged parallel to a rotation axis of a selector lever and to the locking surfaces of the locking element point in the direction parallel to the selector lever longitudinal direction. As a result, any point of the locking surfaces is away from the rotation axis of the locking element at a different lever arm length.
The present invention encompasses all types of automatic transmissions, particularly automatic transmissions having a torque converter, fully automatic and partially automatic gear boxes, automatic converter step mechanisms and variable transmissions with infinitely variable transmission ratios with or without gears.
Additional selection systems are known from U.S. Pat. Nos. 4,721,004; 5,649,452; and 5,695,029. DE 196 41 706 C1, shows a selection system which has a swivellably disposed selector lever which can be swivelled in the direction from a parking position P by way of a reversing position R into a neutral position (idling position) N in which the torque transmitting of the vehicle transmission is interrupted, and into at least one forward driving position D. For the N and P positions, locks are provided which act as a function of certain operating conditions.
In the parking position P, a locking of the known selector lever is required as long as the vehicle brake is not operated and the ignition key is not situated in the ignition lock (or the ignition is not switched on). As soon as the ignition key is situated in the ignition lock (or the ignition is switched on) and the brake is operated, the selector lever is to be released. In the following description, this function will be called a P-lock.
A lock is also provided for the operation of the known selector lever from the neutral position N into the reversing position R. This lock is to be active as long as the vehicle has not yet fallen below a defined limit speed. In the following description, this function will be called an R-lock. However, an operation of the selector lever from D to N must not be hindered by these locks. These functions are described in DE 196 41 706 C1.
JP 3-239868 A describes an arrangement in which locking devices of the selector lever which are assigned to the parking position P and to the reversing position R can be unlocked by exciting a solenoid. The locking function is generated by spring force. In the event of a current failure in the overall vehicle system, it is therefore not possible to bring the selection system into the parking position P. It is therefore also not possible to park the vehicle in a secured manner because the ignition key can be taken out of the ignition lock only in the P-position of the selector lever. In addition, a selection system is described in JP 6-117526 A in which a selector lever is fixedly connected with a locking gate which is provided with stop cams.
DE-A-41 18 519 describes a selection system for an automatic transmission which has a selector lever which, by swivelling about a swivel axis, can be adjusted in one direction from a neutral position N into a forward position D and beyond it to one or several low-gear shifting positions (1, 2) and in the opposite direction to a reversing gear position R and beyond it to a parking position P. A manual backshifting from a higher-ratio gear to a lower-ratio gear will then be automatically blocked if a critical condition would occur for the vehicle as the result of such a backshifting.
The actuators or control elements, which bring the above-mentioned locking devices into the locking and the unlocking position, are preferably electromagnetic control elements and springs but may also be other elements, such as hydraulically or pneumatically operated elements. It should not be possible to unlock the locks at the selector element by a driver's manual operating force, if the operating conditions which are required for an unlocking do not exist, e.g., a driving authorization is given by the driver; the ignition key is in the ignition lock; the vehicle brake is activated; a vehicle brake lock is not unlocked; and/or the vehicle speed is below or above a defined limit value.
A control element must also be able to unlock the lock if the corresponding operating conditions have been met but the driver exercised a manual operating force on the selector element before these operating conditions had been met. In this case, there is the risk that the mechanical locking elements are compressed so much by the manual operating force on the selector lever that they can no longer be torn apart or separated by a control element, or the control element would have to have a size which is not acceptable with respect to the required space and weight or because of the operating heat generated thereby. A larger electromagnetic control element generates a greater amount of heat.